SPECTROPHOTOMETRIC DETERMINATION OF ERYTHROMYCIN ETHYLSUCCINATE BASED ON THE CHARGE TRANSFER REACTION BETWEEN ERYTHROMYCIN ETHYLSUCCINATE AND PURPURIN

A spectrophotometric method for the determination of erythromycin ethylsuccinate was described in this paper.The method was established based on the charge transfer reaction between erythromycin ethylsuccinate as donor and purpurin as acceptor in water-alcohol medium.The molar ratio and stability constant of charge transfer complex is 1∶1 and 1.9×105,respectively.The apparent molar absorptivity of the color complex is 9.18×103L·mol-1·cm-1 at 546 nm.Beer′s law is obeyed in the range of 0-90 mg·L-1 of erythromycin ethylsuccinate.Correlation coefficient is 0.999 7.The relative standard deviation of six determinations is 1.24% at the concentration level of 40 mg·L-1.The proposed method has been applied to the determination of erythromycin ethylsuccinate in medical tablets giving results in consistency with the results obtained by the pharmacopeia method.